Swage baseplates are widely used in disk drives to attach head suspensions to E-blocks, C-blocks or other actuator arms. Examples of these attachment structures and associated assembly methods are disclosed in the Wang et al. U.S. Patent Application Publication No. 2002/0145830, and the Hanrahan et al. U.S. Pat. Nos. 6,033,755 and 6,183,841, all of which are incorporated herein by reference.
Briefly, baseplates include a generally flat flange and a tubular boss tower extending from the flange. The flange is typically welded to a mounting region of the suspension. The boss tower is sized to fit within an opening in the actuator arm to which the suspension is to be mounted. During the swaging process a ball is forced through the boss tower, thereby forcing the outer surface of the boss tower into frictional engagement with the inner surface of the opening in the actuator arm. The baseplate and attached suspension are thereby securely fastened to the actuator arm. Unfortunately, this swaging process can result in deformation of the actuator arm. This actuator arm deformation can cause changes in the desired positional orientation of the suspension on the actuator arm, known as z-height variations, and changes to the desired spring characteristics of the suspension, known as gram changes. Z-height changes depend to some degree on suspension parameters such as spring rate and effective length, but by way of example, changes in the range of 0.005–0.015 mm have been observed in suspensions having a 20 N/m spring rate. Also by way of example, gram load changes in the range of 0.1–0.3 gram and have been observed. These swaging-induced z-height variations and gram changes can detrimentally affect the operational performance of the suspensions. These problems have been observed to be especially prevalent in arms, typically at the ends of a multi-arm stack, having only one suspension swaged thereto.
There is, therefore, a continuing need for disk drive suspension structures and assembly methods that minimize z-height variations and gram changes. Baseplates that contribute to these objectives by minimizing swaging-induced deformation to actuator arms during the swaging process would be especially desirable.